fix

Author: sreichel

app/code/core/Mage/Adminhtml/Block/Sales/Order/View/Tab/History.php

@@ -109,7 +109,7 @@ public function getFullHistory()
             );
         }
 
-        usort($history, $this->_sortHistoryByTimestamp(...));
+        usort($history, [self::class, '_sortHistoryByTimestamp']);
         return $history;
     }
 
@@ -284,7 +284,7 @@ public function isCustomerNotificationNotApplicable($historyItem)
      * @return int
      */
     // phpcs:ignore Ecg.PHP.PrivateClassMember.PrivateClassMemberError
-    private function _sortHistoryByTimestamp($a, $b)
+    private static function _sortHistoryByTimestamp($a, $b)
     {
         $createdAtA = $a['created_at'];
         $createdAtB = $b['created_at'];